Theoretical calculations of the minority-carrier diffusion length in high-internal-quantum-efficiency GaAs

An explicit expression for the GaAs minority-carrier diffusion length, taking into account phenomena of photon absorption reemission, is deduced. A simpler approximate expression, valid for internal efficiencies larger than 0.9 and introducing an error less than 10%, is also obtained. The application of the deduced expressions to practical devices is discussed. It is concluded that such application is not a straightforward matter, as we must take into account the probability that some of the generated photons leave the active region of the device.